Rise in kids' food allergy rates called dramatic and unexplained

Better awareness unlikely to account for surge, study says

November 18, 2009|By Shari Roan, Tribune Newspapers

The number of children who have food allergies not only is increasing, it encompasses 4 percent of all kids in the United States, according to an analysis of four large national surveys published Monday in the journal Pediatrics.

The study is the first to make a broad estimate about the prevalence of food allergies among U.S. children and supports previous studies suggesting rates are rising rapidly for reasons that are unclear.

The data suggest a real surge in illnesses and not just better awareness and diagnosis of the problem, said the lead author of the study, Amy Branum, of the National Center for Health Statistics.

"To see almost a tripling of visits in a 13-year period is pretty good evidence that this isn't just parents hearing about food allergies on the news and then thinking their children have it," Branum said. "We used four different surveys, and to see an increase in food allergies in all of those surveys is very telling."

Most of the data were drawn from surveys of children's parents. Using medical records from 2005-06, however, researchers also found that 9 percent of children in one survey tested positive for IgE antibodies to peanuts. IgE antibodies are found in the lungs, skin and mucous membranes usually in response to food allergies.

The study also suggests potential racial differences among children with food allergies. Although Hispanic children had the lowest prevalence of food allergy in 2007 compared with other racial groups, they had the greatest increase in reported allergies over the period studied.

"It's very possible that what we're seeing with Hispanic children is more awareness of food allergies," Branum said.

The evidence of widening food allergies among all age and ethnic groups is worrisome, said Dr. Scott Sicherer of the Jaffe Food Allergy Institute at Mount Sinai School of Medicine in New York.

"It's likely there is a real increase," said Sicherer, who was not involved in the current study. "If you ask physicians, school nurses, the Food and Drug Administration, industry, there is an impression that there are more children with allergies than before. Asthma, eczema and hay fever are also going up. The message seems to be we need to start believing this and looking for answers instead of worrying about just how many people are affected. It's a lot."

Several theories have been proposed to explain why more children have food allergies, Branum said.

One prominent theory is the hygiene hypothesis, which is based on the notion that today's children are less exposed to germs and other disease-causing substances than previous generations -- preventing their immune systems from developing normal responses to invaders. The immune system then overreacts to relatively harmless substances.

Studies are needed to determine who is most likely to develop allergies and why, Branum said.

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Key findings

Self-reported allergies increased 18 percent between 1997 and 2007.

Health care visits for food allergies in children nearly tripled between two time periods studied: 1992 through 1997 and 2003 through 2006.

Race factor: Among non-Hispanics, allergies to milk, peanuts and other foods were more prevalent in black children than white children.